rotary selector switch

salomonander · Aug 23, 2012

Hey Ian

i did come up with something yesterday. maybe you can give me some feedback?
i attached a drawing to make things easier to understand:

i use 3 dpdt relays per channel (L/R, group 1/2, group 3/4). by default (when not energized) they pull their bus feed resistors to ground.... so no signal goes anywhere. i also have a 1p3t position rotary switch (group selection switch) that allows to energize one of the relays at a time.
so the channel would be routed to one bus only, while all other bus feed resistors are grounded.
in order to achieve a mute i run all the relays power supply through one jfet which i can trigger via a logic signal. when the jfet is energized it cuts all power to the relays - full mute.
what do you say?

ps: the "group module" plan shows no actual relay connections. just how i want to energize them. the relay wiring is in the next plan.

salomonander · Aug 23, 2012

this is the relay wiring (for group 1/2). please let me know if all of this is completely wrong. im a beginner and still learning.

ruffrecords · Aug 23, 2012

Hi, I just got back from a couple of days holiday!! The logic of your scheme is fine. The only thing to watch is to ensure the FET can take the relay voltage/current and that is is adequately protected from the reverse switch off voltage which it looks like the diodes take cars of. It might also be easier from the point of view of switching the FET to put it in the -ve input connection rather than the +ve but tat depends on the FET you choose.

Cheers

Ian

salomonander · Sep 4, 2012

thanks again
sorry for the late reply i was on a little vacation. i did have one more idea though. maybe someone could let me know if this might work as well?

basically go back to a 3 pole rotary that simply switches the channels signal to one of the busses - therefore leaving unselected busses open. in order to ground them i also connect each bus feed to ground via a jfet. when the jfets are not activated they pull each bus feed resistor to ground. a little trigger voltage is now feed into pole three of the rotary switch. it will close the jfet of the group that is assigned at the time. so when audio is routed to say L/R the L/R jfet is also closed. i tried to make a drawing for better understanding (ps: i onely drew one side of the audio - lazyness).

...in case this might work it would be a lot smaller and cheaper than the relay version.

ruffrecords · Sep 4, 2012

Yes, I think that would work. You arrange the FET bias so they are normally on and only turn one off at a time depending on the switch.

Cheers

Ian

salomonander · Sep 4, 2012

ruffrecords said:
Yes, I think that would work. You arrange the FET bias so they are normally on and only turn one off at a time depending on the switch.

Cheers

Ian

cool. thanks. ill try to beadboard this and see if it works out.